The invention relates to optical signal switching. In particular, the invention relates to switches used to route signals in optical networks.
Optical networks are rapidly becoming the network technology of choice for modem data and telecommunications systems, principally due the inherently high bandwidth and low loss characteristics of optical fibers that carry the data from node to node within such networks. In addition to optical fibers, optical networks employ optical switches at the nodes for routing signals via a plurality of paths or circuits within the network. A current challenge in optical networking is the development of optical network switches that have performance characteristics such as bandwidth, effective bit-rate independence and/or protocol independence consistent with the characteristics of the network that employs the switch.
A relatively new approach to realizing such high performance optical switches is micro-electromechanical systems (MEMS) technology. A simplified geometry indicative of conventional MEMS micromirror optical switches known in the art is illustrated in FIGS. 1A and 1B. The optical switch 10 comprises a rotatable or movable micromirror 12 and a plurality of N optical ports 14i, i=1, . . . , N, rectilinearly arranged along one or more sides of a rectangle 16 surrounding the micromirror 12.
Unfortunately in switches having such geometries with the rectilinear arrangement of ports, accurate control of the orientation angle xcex8i of the micromirror 12, generally necessitates the use of high precision, servo-based mirror-motion control to position the micromirror 12. In addition, the conventional rectilinear geometry produces optical path length differences with respect to various distinct port-to-port connections or switch positions of the switch. Among other things, the path length differences may cause differential defocusing of the optical beam for different switch positions.
Accordingly, it would be advantageous to have an optical switch with a geometry that yielded a more favorable trade-off between orientation angle accuracy and motion control precision. Furthermore, it would desirable for such an optical switch to have optical paths that were not different from one switch position to the next. Such an optical switch would solve a long-standing need in the area of switching for optical networks.
The present invention switches an optical signal between optical ports of an annular array of ports using a movable or rotatable mirror. The rotatable mirror is positioned substantially equidistant from each port of the annular array to direct the optical signal from an input port to an output port of the switch. The optical ports are angularly positioned in the annular array such that a minimum angular resolution of the mirror is optimized.
In an aspect of the present invention, an optical switch is provided. The optical switch comprises a plurality of optical ports arranged in an annular pattern and a rotatable mirror having a reflective surface that is adjacent to the plurality of ports. Each optical port of the plurality is equidistant from the rotatable mirror. In another aspect of the present invention, a method of switching an optical signal is provided. Certain representative embodiments of the present invention along with various features and advantages thereof are detailed hereinbelow with reference to the following drawings.